You've got clients, so you're a contractor, right? Which means you have savings... hopefully?

I'd be straight with them, and tell them you need some time off for personal reasons. Be specific as to how long you want. Help them find a stand-in in the meantime if appropriate. If you deal well with them rather than just going AWOL you stand a good chance of keeping good relationship with them.

I'm really sorry you're going through a hard time. I'm sure you'll pull through it. Hang in there!